A buck converter or step-down DC-to-DC converter is a switched-mode power supply which comprises a storage inductor L, an output capacitor Cout, a semiconductor switch S (which may e.g. be realized as a bipolar transistor or field effect transistor) and a freewheeling diode D for controlling the voltage drop UL across the inductor and thus current flow IL through this inductor. The operation of a buck converter is fairly simple, as it periodically alternates between an on-state where the inductor is connected to an input voltage Uin so as to store electric energy in the inductor and an off-state where the inductor is discharged into a load, such as e.g. an ohmic resistor R. In the on-state, voltage drop UL across the inductor is given by the difference of the buck converter's input voltage Uin and output voltage Uout. As can easily be calculated, current IL through the inductor rises linearly. In the on-state, as freewheeling diode D is reverse-biased by input voltage Uin, there is no current flow through this diode. In the off-state, diode D is forward-biased such that the voltage drop across the inductor is UL=−Uout (when assuming that diode voltage drop UD is neglectable) and inductor current IL decreases.